The present invention is related to a network or a method in a network, the basic conception of which consists in providing processing units as network elements which may be divided into two classes, with the network elements of the first class having a role in the routing of data packets in a network different from the role of the network elements of the second class. The network elements of the first class may be called switches and have the task of routing data packets, i.e. forwarding the same to a neighbouring switch, which is a switch directly connected to a respective switch via a communication line. The switches, however, do not themselves define to which neighbour switch the data packets are to be sent. Rather, they make use of a flow information data base (or forward information data base), e.g. in the form of a flow table providing to a plurality of addresses which might be contained in a header of a data packet in a group of data packets the information about that neighbour switch to which the data packet having the respective address in its header is to be sent. With the switches making use of these flow information data bases, the network elements of the second class, the controllers, are responsible for providing the information or data comprised in the information data base.
In the network, the switches need to be connected to neighbour switches in order to obtain a network of switches. For each switch there might be provided a controller which is connected thereto via a communication line which might be different from those communication lines by which the switches are connected. Moreover, different controllers may be connected to each other via further communication lines which might be different from other communication lines in the network. For example, communication lines may differ from each other by different protocols being needed when communicating via these communication lines.
When routing data packets, or groups of data packets, there might be the need to make sure the routing takes place quickly enough. For example, if the groups of data packets represent audio or video data to be sent via the network, each delay in the flow of data has to be avoided. There is therefore the need to make sure that at least a particular kind of data packets arrives as quickly as possible or at least with a minimum velocity at the end device corresponding to the address to which the groups of data packets are sent.